Right Ventricle Dysfunction in Cardiomyopathy: To Measure Is to Know

Right Ventricular Free Wall Strain and Effect of Defibrillator Implantation in Patients With Nonischemic Systolic Heart Failure

BACKGROUND

Patients with nonischemic systolic heart failure have an increased risk of malignant ventricular arrhythmias and sudden cardiovascular death. Because the risk is less pronounced than for patients with ischemic cause of heart failure more discriminating tools are needed to identify patients most likely to benefit from implantable cardioverter-defibrillator (ICD) implantation. Right ventricular (RV) dysfunction is associated with a worse prognosis, but whether RV free wall strain (RV-FWS) measured with echocardiography can identify the patients most likely to benefit from ICD implantation is not known.

METHODS AND RESULTS

In this extended follow-up analysis of the Danish Study to Assess the Efficacy of ICDs in Patients with Non-ischemic Systolic Heart Failure on Mortality (DANISH) trial, RV-FWS was measured with echocardiography in 445 patients before randomization. RV dysfunction was defined as an RV-FWS of greater than -20%. The primary end point was all-cause mortality. The median RV-FWS was -18% (quartiles -23% to -14%), and RV dysfunction was measured in 255 patients (57%). During a median follow-up of 5.7 years, 170 patients (38%) died. There was a statistically significant interaction between RV dysfunction and the effect of ICD implantation (P = .003), also after adjusting for known cardiovascular risk factors (P = .01). ICD implantation significantly decreased all-cause mortality in patients with RV dysfunction (hazard ratio 0.54, 95% confidence interval 0.36-0.80, P = .002), but not in patients with normal RV function (hazard ratio 1.34, 95% confidence interval 0.84-2.12, P = .22).

CONCLUSIONS

In patients with nonischemic systolic heart failure, RV dysfunction on echocardiography was associated with a greater effect of ICD implantation and could be used to select patients with benefit from ICD treatment.

An Explainable Machine Learning Approach Reveals Prognostic Significance of Right Ventricular Dysfunction in Nonischemic Cardiomyopathy

OBJECTIVES

The authors implemented an explainable machine learning (ML) model to gain insight into the association between cardiac magnetic resonance markers and adverse outcomes of cardiovascular hospitalization and all-cause death (composite endpoint) in patients with nonischemic dilated cardiomyopathy (NICM).

BACKGROUND

Risk stratification of patients with NICM remains challenging. An explainable ML model has the potential to provide insight into the contributions of different risk markers in the prediction model.

METHODS

An explainable ML model based on extreme gradient boosting (XGBoost) machines was developed using cardiac magnetic resonance and clinical parameters. The study cohorts consist of patients with NICM from 2 academic medical centers: Beth Israel Deaconess Medical Center (BIDMC) and Brigham and Women's Hospital (BWH), with 328 and 214 patients, respectively. XGBoost was trained on 70% of patients from the BIDMC cohort and evaluated based on the other 30% as internal validation. The model was externally validated using the BWH cohort. To investigate the contribution of different features in our risk prediction model, we used Shapley additive explanations (SHAP) analysis.

RESULTS

During a mean follow-up duration of 40 months, 34 patients from BIDMC and 33 patients from BWH experienced the composite endpoint. The area under the curve for predicting the composite endpoint was 0.71 for the internal BIDMC validation and 0.69 for the BWH cohort. SHAP analysis identified parameters associated with right ventricular (RV) dysfunction and remodeling as primary markers of adverse outcomes. High risk thresholds were identified by SHAP analysis and thus provided thresholds for top predictive continuous clinical variables.

CONCLUSIONS

An explainable ML-based risk prediction model has the potential to identify patients with NICM at risk for cardiovascular hospitalization and all-cause death. RV ejection fraction, end-systolic and end-diastolic volumes (as indicators of RV dysfunction and remodeling) were determined to be major risk markers.

Right ventricular free wall longitudinal strain and strain rate quantification with cardiovascular magnetic resonance based tissue tracking

Cardiovascular magnetic resonance based tissue tracking (CMR-TT) was reported to provide detailed insight into left ventricular mechanical features. However, inadequate knowledge of the right ventricle (RV) mechanical deformation has been acquired by this advanced technique so far. It was the aim of this study to establish reference values of RV free wall (RVFW) global, regional and segmental longitudinal peak strain and strain rate (LS and LSR), and to investigate the gender- and age-related difference as well as the base-to-apex gradient of RVFW-LS and LSR with CMR-TT. 150 healthy volunteers (75 males/females) were retrospectively and continuously recruited and subdivided into three age groups (G_20–40, G_41–60 and G_61–80). RVFW global, regional (basal, middle-cavity and apical) and segmental LS (GLS, RLS, SLS) along with systolic and diastolic LSR were generated by post-hoc CMR-TT analysis of standard steady-state free precession long-axis four-chamber view cine images acquired at 1.5T field strength. The reference value of myocardial RVFW-GLS was − 24.9 ± 5.2%. We found that females showed more negative GLS than males except in the youngest group, and no age-related difference of GLS was observed in both gender groups. RLS and SLS presented with the same age-related tendency as GLS. The basal and middle-cavity LS were similar between each other and significantly larger than apical LS. RVFW-GLSR resulted as − 1.73 ± 0.58 s⁻¹ and 1.69 ± 0.65 s⁻¹ during systolic and diastolic phases, respectively. The diastolic GLSR of males tended to decline with the ageing and was significantly lower than that of females in G_61–80 group. Regional and segmental LSR showed significant gender-related differences in certain basal and apical region/segments without any age-related effects. CMR-TT overcomes the difficulty in measuring RV global and segmental deformation. The establishment of the vendor-, gender- and segment-specific reference values of RVFW-LS and LSR is essential for the rapid and efficient utilization of CMR-TT modality in the clinical routine.

Assessment of right ventricular function in advanced heart failure with nonischemic dilated cardiomyopathy: insights of right ventricular elastance

BACKGROUND

The right ventriculoarterial coupling (R-V/A), a measure of right ventricular systolic dysfunction (RVSD) adaptation/maladaptation to chronic overload, and consequent pulmonary hypertension, has been little investigated in nonischemic dilated cardiomyopathy (NIDCM). We examined the correlates of R-V/A and traditional echocardiographic indices of RVSD, over the spectrum of pulmonary hypertension and tertiles of mean pulmonary artery pressures (PAPm).

METHODS

In 2016-2017, we studied 81 consecutive patients for heart transplant/advanced heart failure. Inclusion criteria were NIDCM, reduced ejection fraction (≤40%) and sinus rhythm. R-V/A was computed as the RV/pulmonary elastances ratio (R-Elv/P-Ea), derived from a combined right heart catheterization/transthoracic- echocardiographic assessment [right heart catheterization/transthoracic-echocardiographic (RHC/TTE)].

RESULTS

A total of 68 patients (mean age 64 ± 7 years, 82% men) were eligible. After adjustments, R-Elv and P-Ea were higher in isolated postcapillary-pulmonary hypertension (Ipc-PH) than combined-pulmonary hypertension (Cpc-PH) (P = 0.004 and P = 0.002, respectively), whereas R-V/A progressively decreased over Ipc-PH and Cpc-PH (P = 0.006). According to PAPm increment, P-Ea congruently increased (P-Trend = 0.028), R-Elv progressively decreased (P-Trend<0.00)1, whereas R-V/A significantly worsened (P-Trend = 0.045). At the multivariable analysis, a reduced RV longitudinal function (TAPSE<17 mm) was positively associated with R-V/A impairment (<0.8) [odds ratio 1.41, 95% confidence interval (CI) (1.07--1.87), P = 0.015]. R-Elv and P-Ea showed good interobserver reliability [interclass correlation (ICC) 0.84, 95% CI (0.32--0.99), P = 0.012 and ICC 0.98, 95% CI (0.93--99), P < 0.001, respectively].

CONCLUSION

Among NIDCM HF patients, in a small cohort study, RHC/TTE-derived R-V/A assessment demonstrated good correlations with pulmonary hypertension types and RV functional status. These data suggest that R-V/A encloses comprehensive information of the whole cardiopulmonary efficiency, better clarifying the amount of RVSD, with good reliability.